- noun the compression of ground and making it hard, e.g. by driving over it with heavy machinery or as the result of a lot of people walking on it
- noun the act of pressing things together to form one, or of compressing something to make it hard
- The compression of any material into a smaller volume; for example, waste compaction. In specifying compaction of embankment or fill, a percent compaction at optimum moisture content is often used. Another method is to specify the equipment, height of lift, and number of passes.
- The elimination of voids in construction materials, as in concrete, plaster, or soil, by vibration, tamping, rolling, or some other method or combination of methods.